This the first part of the Robotic Arm Project, we started. This Base is using the Planetary Gear Drive: https://www.youmagine.com/designs/planetary-drive. For the Balls in the Bearing Ring, we used 8mm balls you will get them on amazon (https://www.amazon.de/200x8mm-Edelstahl-Katapult-Slingshot-Shooting/dp/B075SZFJ91/ref=sr_1_17?ie=UTF8&qid=1543080012&sr=8-17&keywords=balls+8mm).